1. Field of the Invention
The present invention relates to a light-emitting device epitaxial wafer formed of compound semiconductor crystals, and a light-emitting device.
2. Description of the Related Art
Light-emitting devices formed of compound semiconductor crystals, such as light-emitting diodes (LEDs) produced using an AlGaInP-based epitaxial wafer, are widely used in various applications, such as displays, remote controls, on-vehicle lamps, etc., with increasing luminance.
As a method for growing compound semiconductor crystals, there is metal organic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE) or the like.
In the MOVPE, group III organic metal and group V raw material gases are mixed with high-purity hydrogen carrier gas and introduced into a reaction furnace, and pyrolyzed around the substrate heated in the reaction furnace, thereby epitaxially growing the compound semiconductor crystals over the substrate.
In the MBE, a raw material metal is heated in an ultra-high vacuum to produce a molecular beam, to apply the molecular beam to target substrate crystals to grow thin films.
The compound semiconductor epitaxial wafer refers to a wafer with epitaxial layers formed over a compound semiconductor substrate with the above method. As a typical example of the compound semiconductor epitaxial wafer, there is a light-emitting device epitaxial wafer.
The light-emitting device epitaxial wafer is structured by MOVPE, MBE or the like stacking, sequentially on a substrate, an n-type cladding layer, a light-emitting layer, and a p-type cladding layer.
The n-type dopant of the n-type cladding layer uses mainly Te (tellurium), Se (selenium), and Si (silicon). Of these, using Te or Se in epitaxial growth causes Te or Se to remain in a reaction furnace, so that in subsequent growth, the remaining Te or Se is taken into the crystal. This phenomenon is called the memory effect. Experientially, Si causes no memory effect phenomenon.
Refer to JP-A-7-94780, JP-A-2004-241463, JP-A-10-270797, JP-A-2000-31597 and JP-A-2004-63709, for example.
The light-emitting device is presently required to be lower in cost and more stable in performance, because of increasing applications expected and competition with the prior art.